Ball transfer or caster unit



Sept. 16, 1969 E' 5, CMN ET AL 3,466,697

BALL TRANSFER OR CASTER UNIT Filed May 10, 1968 3 Sheets-Sheet l INVENTORS EARL S. CAIN JEROME A. CARLSON GEORG EGOODRICH gm'mm v A T YS Sept. 16, 1969 E. s. CMN ET AL n 3,466,697

BALL TRANSFER OR CASTER UNIT Filed May l0, 1968 3 Sheets-Sheet 2 'II'.V'I'II'I'I INVENTORS EARL S. CAIN JEROME A. CARLSON E ORGE E. GOODRICH F/G. B/ MMTWS Sept; 16, 1969 E, s, CMN ET AL 3,466,697

BALL TRANSFER on oAsTER UNIT Filed May 1o, 1968 s sheets-sheet s 94 #MAAM/Mz; 92 los lo? 109108 los Mms United States Patent O 3,466,697 BALL TRANSFER OR CASTER UNIT Earl S. Cain, Woodside, Calif., Jerome A. Carlson, Mercer Island, Wash., and George E. Goodrich, San Carlos, Calif., assignors to Bearings, Seals & Gears, I nc.,

Redwood City, Calif., a corporation of California Filed May 10, 1968, Ser. No. 728,196

Int. Cl. B60b 33/08 U.S. Cl. 16-26 9 Claims ABSTRACT F THE DISCLOSURE A spring-loaded ball transfer or caster unit including means for releasably securing the unit to structures with which it is associated and/ or means serving to limit movement of the ball responsive to a load applied thereto.

BACKGROUND OF THE INVENTION This invention relates generally to a ball transfer or caster unit and more particularly to a unitvparticularly adapted for use in cargo handling systems where containers are moved over transfer pallets or floors.

Prior art ball transfer units employed for this purpose have been secured to the floor or pallet by screws or bolts. As a result, considerable time is required to replace a damaged unit. Another difficulty with many prior art ball transfer units is the fact that they make no integral provision for load distribution among units on which the cargo is resting. Thus, a unit which projects a greater distance above the floor will carry a larger proportion of the total load than other units. Where spring-loaded units are employed to overcome the above excessive loads, the springs can be damaged by overload and, therefore, destroy the functionality of the unit.

SUMMARY OF THE INVENTION AND OBJECTS It is an object of the present invention to provide an improved ball transfer or caster unit.

It is another object of the invention to provide a ball transfer or caster unit including releasable latching means for securing the transfer unit to an associated structure.

It is another object of the present invention to provide a spring-loaded ball transfer or caster unit including positive stop means for limiting the compression of the spring.

It is a further object of the invention to provide a ball transfer or caster unit with predetermined dimensions and number of support balls to provide support for the ball and smoothness of operation of the unit.

It is a further object of the present invention to provide a ball transfer or caster unit comprising a cylindrical, square, or other housing adapted to receive and hold a ball transfer sub-assembly and a spring for urging the subassembly upwardly. Further, the ball transfer unit includes releasable retaining means for removably holding the unit in associated apparatus for easy insertion and removal.

The foregoing and other objects of the invention will be more clearly understood from the following description taken in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWING FIGURE 1 is a sectional view of the preferred embodiment of the present invention.

FIGURE 2 is a top view of the ball transfer unit of FIGURE 1.

FIGURE 3 is a bottom view of the ball transfer unit of the present invention.

FIGURE 4 is a plan view showing the position of the support balls when a moving load is presented to the load transfer ball.

Patented Sept. 16, 1969 FIGURE 5 is a plan view showing the position of the -support balls when the load transfer ball is stationary.

FIGURE 6 is an enlarged View of the portion 6-6 of FIGURE l showing details of the latch assembly.

FIGURE 7 is a sectional view taken along the line 7 7 of the stop ring shown in FIGURE 8.

FIGURE 8 is a front elevational view of the stop ring shown in FIGURE 5.

FIGURE 9 is a schematic diagram showing a floor section or pallet incorporating a plurality of ball transfer units.

FIGURE 10 is a side elevational view showing a container riding on the ball transfer units of the iloor or pallet.

FIGURE ll is an enlarged view of a portion of the pallet or floor showing particularly the cross beams and the opening for receiving the ball transfer unit.

FIGURE l2 is a View, partly in section, of another ball transfer unit incorporating the present invention.

FIGURE 13 is a sectional view of a low profile ball transfer unit in accordance with the invention.

FIGURE 14 is a sectional view of still another ball transfer unit incorporating the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIGURES 1-4, the ball transfer unit shown includes a cylindrical outer housing 11. One end of the housing is stepped inwardly to form a rst stop 12, a smaller cylindrical portion 13, a second stop 14, and a bottom portion 16. The bottom portion 16 is adapted to register with an opening formed in the ball transfer unit support. The bottom portion includes a pair of projections 17 and 18 adapted to t into and register with notches formed in the receiving structure to thereby orient the ball transfer unit.

A load spring 19 is disposed coaxially Within the housing 11. One end of the spring abuts the stop 12. A cylindrical spring guide and stop 21 are disposed concentrically within the housing 11 and define along with the housing a pocket 22 for the spring 19. The lower end of the guide 21 cooperates with portion 13 to form a bottom guide. One end of the guide 21 is bent inwardly to form a flange 23 which is adapted to abut the stop 14 and limit axial movement of the guide 21. The guide 21 also guides the l ball sub-assembly (to be described) during its telescoping movement and provides a positive stop to support the load whereby the spring is not damaged by excessive load. The guide also prevents tipping of the spring or clashing of coils to allow it to expand and return the subassembly without restriction or restraint.

The other end of the guide 21 is bent outwardly to provide a shoulder 24 which engages the upper end of the spring. A bent lip 26 formed on the guide serves to hold the ball subassembly in an assembled relationship. The -ball sub-assembly includes a support ball cup 27 having an outwardly extending rim 28 which rides on the shoulder or abutment 24.

A plurality of support balls 29 are carried in the cup 27. A transfer ball 31 is nested upon and carried by the support balls 29. A ball retainer and cover 32 serves to retain the transfer ball 31 and support balls 29. The member 32 includes a cylindrical portion 33 which serves as a top guide. One end is bent inwardly to provide a retaining ring 34 for `the transfer ball 31. The other end is bent outwardly to form a shoulder 36 which serves to retain the support balls 29. The shoulder rides on the lip of cup 27. The retainer 32, cup 27 and the spring guide and stop 21 are held in assembled relationship by the lip 26 of guide 21.

The transfer ball sub-assembly is held within the housing by means of a retainer ring 37. The retainer 37 is in the form of a ring and includes a lower lip 38. The other end of the housing 11 is bent over and engages the lip to hold the retaining ring. The spring 19 is selected such that when the ball transfer unit is assembled, the spring is under a predetermined compression to provide an initial force urging the sub-assembly and ball upwardly.

We have discovered that there is a preferred relationship between the number of support balls (n) and the analytical cut depth (h) to maintain smoothness of rotation of the load transfer ball with given load, cup curvature, rotational speed of the load transfer ball and ratio of support ball diameter and load transfer ball diameter.

FIGURES 4 and 5 are plan views showing positions of the support balls for a rotating load transfer ball and a stationary load transfer ball, respectively. It is noted from FIGURE 4 that for optimum smoothness and minimum friction under load, there must be a sufcient number of support balls to keep the loaded ball zone, Z, full of support balls. Too yfew will cause the load transfer ball to rotatably drive the support balls from underneath it in the circulation pattern shown. This would cause the load ball to become unsupported, thereby yielding towards the cup and impeding the entrance of support balls beneath it with a resultant jumping and scul'ling back into normal position again.

Too many support balls for the available circulation space causes jamming and scuiiing of the load ball also. There is an orifice O, FIGURE 4, through which the support balls must ow on each side of the load transfer ball as shown. There must Ibe open volume space for the balls to move into after they have left the loaded zone; otherwise, they will produce a jamming pattern preceding the orilice, thereby jamming into the load zone to cause the load ball to jump and scuf and try to ride out of the cup.

This general pattern of support ball motion holds for uniform driven rotation of the load ball. However, when the load ball is caused to twist or spin rather than rotate about a horizontal axis, the support flow pattern changes from one with approximately half the balls on each side to a plurality on the side of the direction of spin. This tends to clog the inadequate orifice opening. Such spinning characteristic is typical in practice when the plane or base of the support pallet or container is not perpendicular to the vertical centerline of the cup. Of course, the rate of rotation and/or spinning is another relevant factor since it takes time for the balls to move through the circulation pattern.

The preferred percentgae of ll can be determined in several ways. The following relates the total cup analytical surface available (SC) in the spherical segment formed by the support ball centers and an aggregate projected area (SB) of the support balls.

In a support ball transfer unit assembly as shown in FIGURES 1-3 having the following dimensions:

Rc=.638 in.

RB=.0625 in. x=.5125 in. h=.450 in.

The unit performed smoothly under load with between 58 and 72 load support balls which gives a =ll of between 43.5% and 54%. Operating just short of the maximum usable k allows for manufacturing tolerances; thus the choice of 70 balls and k=52.5% nominal was found satisfactory.

We have found that the following ranges are preferable:

load ball radius (R) support ball radius Usefu1 Load Range =P/n=.05 to 5.o (pounds/bau) where P=pressure on support load (pounds) Rc 2(Rl-RB) %=50 to 53 (percent of reference ball dia.)

Percentage 11=k=5 0-5 8%. Load Ball Rotation or spin speed=0l000 r.p.m.

The above assumes 4rigid geometry for all the components of the ball transfer unit. If the components are exible plastic or elastic, then the above applies to the resultant condition of geometry.

Further, in accordance with the present invention, there are provided means for releasably inserting the ball transfer units into associated equipment. The securing or latching means shown includes a lock bolt 41 held in a cylindrical well 42, FIGURE 6. The bolt 41 includes a well 43 for receiving coil spring 44 which urges the bolt 41 outwardly into a locking position. Stop means are provided for limiting the movement of the bolt outwardly. In the example shown, the stop means comprises a stop ring 46, FIGURES 6, 7 and 8, which is adapted to receive the bolt. The bolt is then staked` into the ring by deforming the portion 47 so that it extends upwardly into the detent 48. The ring includes an upwardly extending finger or tab 49 which can be engaged with a screwdriver or other tool to compress spring 44 and move the bolt into a retracted position. Thus, the bolts may be retracted by a screwdriver, a pair of pliers or other suitable means.

In FIGURES 9 and 10, there is shown a ball transfer pallet or floor S1 supporting a plurality of spaced ball transfer units 52. A container 53 is shown riding over the ball transfer units. It is apparent, since the ball transfer units are nondirectional, that the container 53 may be moved in any direction. An enlarged view of a portion of the oor or pallet shown in FIGURES 9 and 10 is shown in FIGURE 11. The pallet includes a plurality of U-beams 54 which extend across the pallet. Skins 56 and 57 are secured on each side of the beams 54. The upper skin S6 is shown with an opening 58 which accommodates the ball transfer housing 11. The lower skin is shown with an opening 59 which accommodates the lower end 16 of the ball transfer unit and which includes locating notches 61 whereby when the ball transfer unit is placed into the openings 58 and 59 and properly oriented, the projections 17 and 18 fit into notches 61 and the bolts 41 extend under the skin 56 to secure or latch the unit. Forces exerted on the ball transfer unit are transmitted through the housing 11 to the beam 54. The weight of a container is transferred equally amongst the various ball transfer units since when the Weight exceeds the preload on the spring, the ball transfer unit will be depressed thereby allowing some of the weight to be carried by adjacent units.

In FIGURE 12, there is shown another ball transfer unit in accordance with the invention. The unit includes an outer housing 60E having a lower in-turned portion 62 Bau Ratio =5 to 2o Cup Curvature f= forming a stop for the coil spring 63. A spring guide and stop 64 is disposed coaxially within the housing. The upper portion of the guide 64 is bent inwardly to form a step 66 which engages the upper end of the spring 63. The guide then extends upwardly to define a rim 68 which engages the lower side of the lip 69 of the ball cup 71. A ball retainer 72 serves to retain the transfer ball 73. The guide and stop 64, ball cup 71 and retainer 72 are secured together by ring 74. As before, the transfer ball 73 rides on a plurality of supports balls 75.

The subassembly is retained within the housing 60 by means of a retaining ring 76 which includes an in-turned lip 77 engaging the out-turned housing lip 78. A bolt 81 is accommodated within wells formed in the retaining ring. The bolt is spring-loaded by means of a spring 82 and is retained by means of a screw 83 which is threadably received by the bolt. The screw 83 may be engaged by a sharp tool to retract the lock bolt.

FIGURE 13 shows a low profile ball transfer unit of the type described with respect to FIGURES 1-8. Like reference numerals have been applied to like parts. The housing 11a includes an in-turned flange 12a forming a spring stop and also the means for transferring weight to an associated cross beam. The spring guide and stop 21a has a lower portion adapted to abut the stop 12a. Thus, the in-turned portion of the outer housing serves as the spring stop, the overload transfer means, and also as a positive stop for the spring retainer and guide. Under normal operation, the spring transfers the applied load. When the unit bottoms under overload or excessive shock, the spring turns would overlap and bind without the overload transfer means. In other respects, the low profile unit is the same as previously described.

Referring to FIGURE 14, there is shown still another embodiment of the invention. The ball transfer unit is shown accommodated in a pallet or floor including an upper skin 86, a lower skin 87 and a cross beam or separator 88. The ball transfer unit includes an outer housing 91 which includes a first step portion 92 at one end forming a shoulder and spring stop or abutment, and a portion 93 adapted to t within the opening 94 formed in the lower skin. A cylindrical spring guide 96 is disposed within the housing and serves to limit the movement of the ball transfer unit downwardly into the housing. The guide 96 includes a stop 97 which is adapted to receive and hold the support ball cup 98 by its rim or lip 99. A transfer ball retainer 101 retains the ball 102 and is held against the cup 98 by means of the lips 103 formed in cut-out portions of the guide 96. The complete assembly is retained within the outer housing by means of a top access snap ring 104.

The ball transfer unit is removably held in the floor or pallet by means of retractable latches 106 which are accommodated in wells 107 formed in the downwardly extending portion of the housing 91. The latches are urged outwardly into an engaging position by means of the spring 108 acting against the latches via the guides 109 and 111. The assembly can be released by inserting a tool between the housing and the spring guides 109 and 111 to urge the guides inwardly to retract the latches and release the ball transfer unit.

Thus, there is provided a ball transfer unit which is easy to assemble and simple in construction. The ball transfer unit includes provisions for limiting the movement of the ball into the unit. The ball transfer unit also includes quick-release latching means whereby the ball transfer unit can -be rapidly replaced by employing a simple tool.

What is claimed is:

1. A ball transfer unit comprising a housing having a stop at one end, a spring disposed in said housing with one end engaging said stop, guide means arranged inwardly of said housing and including abutment means for engaging the other end of said spring, a load transfer ball cup, a plurality of support balls disposed in said cup, a load transfer ball nested in and carried by said support balls, retaining means for retaining said transfer ball and said support balls, means for securing said retaining means and ball cup with respect to said guide means to form a subassembly, and means acting between the other end of said housing and said subassembly for holding the subassembly in the housing, said guide means and said housing being so dimcnsioned that after a predetermined movement of said subassembly in said housing, said guide means engage said stop of said housing to limit movement of said subassembly into said housing to accommodate overload without damage to said spring.

2. The ball transfer unit of claim 1 wherein said guide means includes portions spaced inwardly of said housing to dene therewith a pocket and wherein said spring is disposed in said pocket.

3. The ball transfer unit of claim 1 wherein said retaining means includes at one end an outwardly extending flange extending across the space between said load transfer ball and said ball support cup for holding said support balls in said ball cup, and including at the other end an inwardly extending ange terminating closed adjacent the surface of said load transfer ball for retaining said transfer ball with respect to said support balls.

4. The ball transfer unit of claim 1 wherein said ball cup includes an outwardly extending lip, said retaining means including an outwardly extending flange adapted to rest on said lip, and wherein said securing means xedly secures said flange to said lip.

5. The ball transfer unit of claim 4 wherein said securing means is integral with said guide means.

6. A replaceable ball transfer unit comprising a housing having a stop at one end, a spring disposed on said housing with one end engaging said stop, guide means arranged inwardly of said housing and including abutment means for engaging the other end of said spring, a load transfer ball cup, a plurality of support balls disposed on said cup, a load transfer ball nested in and carried by said support balls, retaining means for retaining said transfer ball and said support balls, means for securing said retaining means and ball cup with respect to said guide means to form a subassembly, means acting between the other end of said housing and said subassembly for holding said subassembly and said housing, and latching means carried by said unit and projecting outwardly therefrom for engagement with associated supporting structure, said latching means being retractable to release the \ball transfer unit from the supporting structure.

7. The ball transfer unit of claim 6 wherein said latching means comprises retractable latches carried by said securing means.

8. The replaceable ball transfer unit of claim 6 wherein said latching means comprises retractable latches carried by said housing.

9. The replaceable ball transfer unit of claim 6 wherein said securing means comprises a retaining ring secured to said housing and wherein said latching means are carried by said retaining ring. 

